My Experiences with Discus - Part II 1

My Experiences with Discus – Part II

Well, this is where the fun really begins. The mechanics of the way that discus reproduce is much the same as any other South American cichlid. However, it is the little peculiarities that some pairs have, that make things interesting. Discus have a reputation for being difficult to breed, but once you gain a little understanding into their traits, then the job does get easier. At this point I would like to reinforce a statement I made in my opening paragraph of Part 1 of this series: this article is not written by an expert! There are many things, that I still have to learn about these fish, but I am happy to pass on some of the traits of pairs or individuals, that I have had or witnessed.

Discusvissen verzorgen hun nest met eieren
Discusvissen verzorgen hun nest met eieren

Firstly the “textbook case”. After growing up a group of young Discus two individuals begin to swim together away from the rest of the group. These fish can usually be seen feeding together and generally staying in close proximity to each other. Later it is observed, that these fish are guarding one end or section of the tank and then they start cleaning a spawning site. This could be the leaf of a plant, a flowerpot, a piece of slate or the side of the tank.

One evening the fish can be seen making practice passes over the spawning site. Soon actual spawning takes place. The female deposits small amounts of eggs in rows and the male follows behind her to fertilise the eggs. This event lasts about an hour after which the pair guards and fans the eggs taking turns at this chore. After two days of this the eggs hatch and the parents help the emerging babies from the eggs and transfer them to a second site.

Another two days pass and the first babies are beginning to swim freely. The parents catch these babies in their mouths and spit them back into the remaining mass of young still left on the spawning site. Finally this task becomes impossible and a tiny school of fry begin to feed from the sides of the parents.

Common problems

Sounds wonderful, doesn’t it?! Well, sorry to bring you back to reality but this type of pair is very rare. Keep this in mind, when next you see “definite breeding pair” written on a shop tank. More often you may experience some of the things, but free-swimming fry is not always the outcome. It is your ability to assess problems as they arise that will bring your success rate up:

  • Starvation:  Until free-swimming, the babies don’t seek their parents to feed from their sides. The babies have only a matter of hours to find the parents and start feeding. If this doesn’t take place, the babies will die. All you can do is hope that it doesn’t happen again.
  • Fighting amongst parents: There are many reasons for this. Jealousy is a common one. One partner wants to take charge of the entire mob itself. There are many solutions to this. Sometimes, leave them to work out their differences, sometimes they must be separated for the duration of that spawn or just for a couple of days. The decision must be made by you based on the action of the fish in your tank, but if fighting is not sorted out within a day or so, then it usually ends in the eggs or fry being eaten.
  • Infertility: Infertility can be a temporary or permanent problem. Temporary infertility can be caused by bad diet or recent medications or overspawning. Time and good diet will cure this. Permanent infertility is rare but can be caused by overuse of antibiotics, or damage by internal parasites. I have only had one fish that was infertile and it was relegated to the display tank.
  • Pairing of two females: Two females often pair up and go through all the motions of successful breeding, but the eggs are not fertile. Sometimes both females spawn simultaneously and sometimes one this week and the other the next. If you can watch them spawn you can usually confirm this. The presence of males in the tank does not seem to affect the practice, but splitting them up and introducing them to males can form pairs and lead to success.
  • Non-breeders: Sometimes after all your efforts, an unsuccessful spawning still takes place. Also some fish never show any signs of wanting to breed. These fish can still make great display fish. Not all fish will breed, so recognise this if it happens and don’t waste your time “flogging a dead horse”.

Raising the fry

Now that all the doom and gloom has been discussed, what happens when the spawn is successful? Well, for the first 4 – 5 days other than feeding the parents and changing water – nothing. The fry feed only from the parents for the first few days. At about day 4 of 5 newly hatched brine shrimp can be introduced. Remember, start with small amounts and build up to larger amounts and more often. The fry will continue to feed off the parents as well as the shrimp for about 2 – 3 weeks, if allowed. However, at about 7 to 10 days after free-swimming it is best to separate the babies from the parents. The risk of parasites being transferred from the parents increases the longer you leave them together. Healthy growing fry should have no trouble adjusting to life without the parents. They will feed on brine shrimp as a basic food and microworms as a supplement, one feed every day. Daphnia and then small mosquito larvae can be added to their feeding program when you notice that their mouths are big enough to swallow them. At about 4 weeks flake food can be introduced, but it may take a while before they take it readily.

Grated frozen beef heart can be started at about 10 cent piece body size, but start at once a day for the first week and then build up to three times a day. By the time they reach 20 cent piece body size, the brine shrimp can be discontinued. Baby discus will eat newly hatched brine shrimp until they are about 50 cent body size, if given it every day. If you stop feeding it for a few days, then they don’t usually go back to it. I usually don’t stop the shrimp until they are feeding on frozen bloodworms, beef heart and flake.

Selling your Discus

Symphysodon discus fry in a grow out tank
Symphysodon discus fry in a grow out tank

So, you have been through all these trials and tribulations and you have spare fry to sell. Check out the prices in the shops and decide what you want for your fish. Don’t be afraid to ask a higher price than similar fish from overseas. Your fish probably have less disease and parasites and are more likely to survive in our water conditions than those from overseas. The best size to sell your fry is at about 50 cent piece size or larger. By this size they should be starting to get colour through the body (if they are turquoise etc.) and are minimum size that the shops will want. You can also grow some to medium size (about 6 months old) and sell them at a higher price.

Diseases and Medications

One thing I have learnt by keeping Discus is that they don’t usually just die for “no reason”.  In most cases there is some sign that something is wrong. When I ignored these signs, I lost fish. Some of the diseases and parasites I have encountered are described below.

  • Hole In The Head Syndrome:  This is a disease often associated with Discus, but it also affects Geophagus species, Uaru amphiacanthoides and Astronotus ocellatus. If treated correctly it need not be a problem. I left untreated, it can cause permanent scarring and even death. The most important treatment is heat treatment. Over a couple of days raise the temperature from 30C to 36C. Additional aeration will be required to ensure adequate oxygen supply. This temperature must be maintained for 8 to 10 days for full recovery, however, the temperature must be dropped if the fish goes into stress. In addition to heat, the fish can be given Flagyl (Metronidazole) orally once every three days for the duration of the heat treatment. See next paragraph for the method.
  • Internal parasites: Internal parasites in the gut can be assumed, if the fish becomes emaciated or produces white, jelly-like faeces. I have no idea of what species of parasites are infecting our fish, but in most cases heat treatment (as for Hole-In-The-Head Syndrome) and Flagyl given orally cures the fish. To treat the fish, assuming the fish is still eating, soak some live tubifex worms or black mosquito larvae in a solution of 10 ml of liquid Flagyl to 200 ml of water for about one hour. Then feed the worms or wrigglers to the fish. This treatment can be repeated every 2 to 3 days for 10 days. If the fish is not eating, then the job is a little more difficult. I have had success by removing the fish from the water and placing it on a wet towel and injecting (using a syringe without needle) the medication down its throat. I use a 2 ml syringe and a mixture of 1 part liquid Flagyl, 2 parts of Liquifry (to try and get the fish’s strength up) and 3 parts water. Before returning the fish to the tank wait for the fish to swallow. It is normal for excess medication to be expelled from the fishes gills and mouth. This treatment can be done twice a day, until the fish shows signs of recovery. The treatment of non-eating fish is not always successful.
  • External parasites: External parasites come in many types and I am unsure of exact species. However, I have found by symptoms, that there are differences and different medications are required. Basically I have two main medications for use for external parasites.* Para-Ex (Wardley’s), which I use for fish that are scratching themselves on objects in the tank. I believe this to be skin fluke and use this drug for anything I feel requires mild treatment. Dosage is one tablet for every 40 litres of tank water, repeating every 3 three days for 9 days.* Formalin solution. Formalin is a solution of 35% – 40% formaldehyde and is very powerful (also carcinogenic and a cell toxin, so avoid contact). It is harsher on the fish and the parasite than Para-Ex and must be used with great caution (formalin is used in science to kill and preserve tissue!!!!). This is effective on gill fluke as well as any other external parasites I have found. Dosage is 1 ml to 38 litres. After three days the tank should be filtered with carbon and a medium water change should be performed. Repeat every 3 days for 3 or 4 treatments or re- infestation will occur. When using formalin, the biological filtration will be killed, so mechanical filtration without the use of carbon will be necessary while the mediation is being used. If additional water changes are necessary within the 3 day treatment, then re-dose an amount corresponding to the amount of water changed. i.e. 30% water change add 30% of the dosage of Formalin.
  • Gill fluke: Gill fluke is a common disease in Discus and is worth mentioning separately to other external parasites. In adult Discus, it is usually associated with heavy breathing, however, in fry it causes much greater problems. When young Discus get to around 10 cent piece size, gill fluke may become a problem. The parents carry gill flukes in small amounts all the time and if the parents are left with the babies too ling, after free-swimming, then the parents can pass them on to the babies. The classic symptoms are heavy breathing, and erratic swimming as though the fish has been bitten on the gill by something inside. This can be accompanied by a spasm and sudden paralysis resulting in the fish sinking motionless to the bottom. This condition seems to be brought on by overcrowding and high feeding rates associated with raising the fry, and can be avoided sometimes by spreading the fry out as they grow. The cure is formalin treatment as described above.
  • Bacterial infections: Bacterial infections can strike Discus the same as any other fish and I have found that two medications are good.* The best is Chloromycetin and comes in powder form. The dosage is one teaspoon to 100 litres of water. It is always fast acting and some improvement should be noticed in 8 hours if it is going to work for that condition. A second dose after two days may be needed, but there is no need to remove the previous dose as it dissipates out after 12 hours. It is important to store Chloromycetin absolutely dry and away from light.* The other medication is Oxolinic Acid. A stock solution of half a gram of the powder in 500 ml of de-ionised water can be made up and stored. The dosage is 1 ml of the stock solution to 10 litres of tank water. This treatment is only effective on some types of infections.
  • White Spot and Velvet Disease: These two diseases are rare in Discus due to the high water temperature (30ºC) they are kept at. But if you do happen to get these parasites then heat treatment will cure it without drugs. White spot is treated with 34ºC for 10 days, whereas Velvet Disease is treated for 2 days. Heat treatment can cure many problems, because most parasites can’t withstand high temperatures. Another parasite, which is also treated with heat, is Costia: 33ºC – 34ºC for 4 days.

Where to obtain these medications

* Flagyl in suspension (liquid Flagyl) is a prescription drug from the chemist. A prescription can be obtained from a veterinarian, if required.
* Para-Ex is made by Wardleys and is available from aquarium shops.
* Formalin solution is an antiseptic available from chemists.
* Chloromycetin, can be obtained in capsule form from some chemists of veterinarians and some aquarium shops.
* Oxolinic acid can be obtained through a chemist from chemical supply houses.


When heat treatment is used, use a separate low wattage externally adjustable heater and keep a careful eye on the temperature as often as possible. Make adjustments only if someone is home for a few hours after the adjustment, to minimise the risk of “cooking” your fish.

When administering medications, calculate the tank capacity accurately to avoid overdosing. A good method is to take the internal dimensions in centimetres and multiply the length by width by height to the water line divided by 1000.


Discus are a challenging fish to keep and breed. There is always something new to learn about them and they are rarely boring. I can recommend them to anyone with experience in keeping and breeding other cichlids and if you follow some of the information in this article, you should be able to adequately care for your discus. All the best and I hope that Discus keeping is as pleasurable for you as it is for me.

First publication: Cichlid Circular, New South Wales Cichlid Society, Australia. November 1990
Source: Aquarticles (no longer available)

Also see the first part of this article My experiences with Discus Part I

Leave a Reply

Your email address will not be published.

Leave this field blank

News, Updates and Promotions

Get our BEST updates delivered to your inbox. Join my email list and get our favourite content regularly. 
Unsubscribe anytime.

Join the AquaInfo Community!

Click the image below and join the AquaInfo Community! Connect with other Aquarium enthousiasts wordwide. Share idead and photo's of your tanks, fish, plants, shrimp, lobsters and more!

Aquainfo Community